Method for poly tip shape fabrication and tip shape application

Abstract

A method for fabricating a floating gate. A semiconductor substrate is provided, on which an insulating layer, conductive layer, and patterned hard mask layer are sequentially formed. The hard mask layer and the conductive layer are sequentially etched to form a trench. The exposed conductive layer is oxidized to form an oxide layer. The hard mask layer is removed. The conductive layer where not covered by the oxide layer is removed using the oxide layer as a mask.

What is claimed is:  
     
         1 . A method for fabricating a floating gate, comprising: 
 providing a semiconductor substrate;    sequentially forming an insulating layer, a conductive layer, and a patterned hard mask layer on the semiconductor substrate;    sequentially etching the patterned hard mask layer and the conductive layer to form a trench;    oxidizing the exposed conductive layer to form an oxide layer;    removing the patterned hard mask layer; and    removing the conductive layer using the oxide layer as a mask.    
     
     
         2 . The method for fabricating a floating gate as claimed in  claim 1 , wherein the insulating layer comprises a pad oxide layer.  
     
     
         3 . The method for fabricating a floating gate as claimed in  claim 1 , wherein the conductive layer comprises a polysilicon layer.  
     
     
         4 . The method for fabricating a floating gate as claimed in  claim 1 , wherein the conductive layer comprises a metal layer.  
     
     
         5 . The method for fabricating a floating gate as claimed in  claim 4 , wherein the metal layer comprises Al, Cu, W, WSi, MO, and Fe.  
     
     
         6 . The method for fabricating a floating gate as claimed in  claim 1 , wherein the patterned hard mask layer is a nitride layer.  
     
     
         7 . The method for fabricating a floating gate as claimed in  claim 1 , wherein the oxidization method is thermal oxidation.  
     
     
         8 . The method for fabricating a floating gate as claimed in  claim 1 , wherein the oxide layer is a silicon oxide layer.  
     
     
         9 . The method for fabricating a floating gate as claimed in  claim 8 , wherein an edge of the silicon oxide layer has a Bird's beak shape.  
     
     
         10 . The method for fabricating a floating gate as claimed in  claim 1 , wherein the method of etching is anisotropic etching.  
     
     
         11 . A method for fabricating a floating gate having a tip, comprising: 
 providing a semiconductor substrate;    sequentially forming an oxide layer, a conducting layer, and a nitride layer thereon;    patterning the nitride layer;    sequentially etching the nitride layer and the conducting layer to form a trench;    thermally oxidizing the exposed conducting layer to form a Bird's beak shape edge thereon;    removing the nitride layer; and    anisotropically etching the conducting layer by the conducting oxide layer using the Bird's beak shape edge as a mask.    
     
     
         12 . The method for fabricating a floating gate as claimed in  claim 11 , wherein the conductive layer comprises a polysilicon layer.  
     
     
         13 . The method for fabricating a floating gate as claimed in  claim 11 , wherein the conductive layer comprises a metal layer.  
     
     
         14 . The method for fabricating a floating gate as claimed in  claim 13 , wherein the metal layer comprises Al, Cu, W, WSi, MO, and Fe.  
     
     
         15 . The method for fabricating a floating gate as claimed in  claim 11 , wherein the thickness of the conducting layer is about 500 Å to 50 Å.  
     
     
         16 . The method for fabricating a floating gate as claimed in  claim 11 , wherein the depth of the trench is about 100 Å to 1500 Å.